One knob, labeled DME, controls the audio re-
ception for both DME1 and DME2. When the
DME knob is unlatched (out position) and the
arrow on the knob is centered straight up, the
audio level is at a minimum. Rotating the con-
trol knob in either direction, toward “1” or
“2” will increase the volume for that corre-
sponding channel only.
The audio level pointers on the knobs are il-
luminated for night flight. There are separate
controls for speaker volume and headphone
volume which adjusts the volume level for all
audio buttons selected.
The speaker push-on/push-off selector is com-
bined with the sidetone knob. When the
speaker switch is extended, it turns on audio
to the on-side speaker.
The speaker sidetone audio is controlled by the
speaker SIDETONE volume control and the
SPEAKER volume control for both on-side
and off-side transmit conditions.
The ID/BOTH/VOICE switch is located on
the right side of the audio panel. In the ID po-
sition, the VOR and ADF audio is filtered to
enhance the Morse Code identification and
eliminate the voice signal. In the VOICE po-
sition, the ident audio is filtered to pass the
voice content only and in the BOTH position,
voice and ident signals may be heard simul-
taneously.
The controls for the marker beacon receiver
are located at the bottom of the audio panel.
They include the marker audio volume control
( M K R ) , m a r ke r s e n s i t iv i t y c o n t r o l ( L O
SENS/HI SENS) and marker mute control
(MUTE).The controls on the left and right
audio panels control the left and right marker
beacon receivers respectively. The sensitivity
is controlled by the rotation of the MUTE con-
trol. If either audio panel MKR sensitivity
control is set LO, then both MKR receivers are
set to LO, regardless of the position of the
other audio panel controls. The pilots can tem-
porarily mute the on-side marker beacon re-
ceiver audio ident by momentarily depressing
the spring-loaded MUTE/HI/LO switch.
The INPH (interphone) volume control ad-
justs the on-side headset audio level when the
interphone function is used. The interphone op-
erates on a “hot mic” basis. The interphone is
not available over the cockpit speaker except
when the oxygen mask audio is selected.
The MIC/MASK control allows for micro-
p h o n e a u d i o s w i t c h i n g b e t w e e n t h e
boom/hand-held microphone (MIC) and the
oxygen mask microphone (MASK). When the
switch is latched (depressed position), MIC is
selected and when the switch is unlatched (out
position), MASK is selected. The MASK in-
tercom feature provides interphone audio to
the on-side cockpit speakers during oxygen
mask operation. This speaker audio is avail-
able regardless of the SPKR ON/OFF button
position. Selecting INPH allows adjustable
volume control of the off-side MASK intercom
on the speaker.
Warning system audio signals are input to the
audio panel for dissemination to the crew over
the headphones and speakers. Also, head-
phone, speaker, and microphone audio is out-
put to the cockpit voice recorder (CVR).
Microphone output is also routed to the No. 1
DAU if the airplane is equipped with an op-
tional flight data recorder (FDR).
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
16-13
FOR TRAINING PURPOSES ONLY
FlightSafety
international